The present invention relates to PCM signal recording and reproduction, and more particularly to a PCM signal recording and reproducing apparatus suitable for copying PCM signals.
Of PCM signal recording and reproducing apparatus, there is disclosed in JP-A-59-16111 laid-open No. on Jan. 27, 1984 (Japanese Patent Application No. 57-125565 filed on July 19, 1982) a rotary head type PCM recorder which records PCM signals on a magnetic tape using a rotary head. In the case where a rotary head type PCM recorder having a plurality of rotary heads, for example, two rotary heads, is used, the two heads are mounted on a rotary member each angularly spaced apart by 360.degree./2=180.degree.. A magnetic tape is slantwise wound about the periphery of the rotary member over an angular range less than 180 degrees, for example, 90 degrees. The rotary member is then rotated while the magnetic tape is run in one direction. Then, PCM signals are recorded one track after another on the magnetic tape in the direction slanted relative to the longitudinal direction thereof alternately using the two heads, or PCM signals already recorded on the magnetic tape are reproduced using the two heads.
PCM recorders of this type are advantageous in that high fidelity audio signals can be recorded and reproduced and that signal quality is not degraded even after plural copies. However, the conventional PCM recorders record or reproduce PCM signals using only one magnetic tape, as in the case of the JP-A-59-16111. Therefore, two PCM recorders have been required for copying recorded PCM signals; one for reproducing PCM signals recorded on a magnetic tape, and the other for recording the reproduced PCM signals on another magnetic tape. Further, a high speed copying such as a double speed copying has not been considered.
FIG. 2 shows an example of a record pattern on a magnetic tape recorded by a conventional single PCM recorder of a rotary head type. Reference numeral 1 generally represents a magnetic tape, and reference numeral 30 represents one block. One track is constructed of a plurality of blocks, for example, 128 blocks, including synchronizing signals 31, control signals 32 such as signals associated with PCM signals and a block number, and PCM signals and error correcting code 33 (the latter is used for correcting errors and called parity hereinafter). The format of one block data is disclosed in the JP-A-59-16111.
FIG. 3 is a timing chart for reproducing PCM signals recorded as in FIG. 2. With rotary head type PCM recorders as disclosed in JP-A-59-16111, PCM signals of two tracks are reproduced every time the two rotary heads rotate once as previously discussed. A PCM signal reproduced is temporarily stored in a memory circuit, such as a RAM and thereafter, subjected to error correction and converted into an analog signal to output it. In order to copy the reproduced PCM signal, the PCM signal after error correction is once stored in another memory circuit similar to the above-described RAM where a parity (error correcting code) shown by numeral 33 in FIG. 2 is added. Thereafter, the PCM signal with a parity is applied to a modulating circuit and recorded on another magnetic tape using other rotary heads. Consequently, there arises a problem that the conventional apparatus become expensive. Further, in case of a high speed copying, reproduction, error correction and recording must be carried out at high speed so that signal processing circuits and recording circuits must be accessed at high speed. For instance, in case of a double speed copying, the time required for reproducing and error-correcting PCM signals becomes half, respectively. Moreover, a time for recording is needed so that memory circuits and signal processing circuits must be operated at a double speed or higher. Particularly, in case of error correction, it is necessary to input data from a memory circuit to an error correcting circuit and write the corrected data in another memory circuit, thus causing a number of accesses to RAMs and therefore leaving only a short time for error correction.